Ringing arrangement for multiplex circuits



.July 91; 1923. 1,499,299

J. DAVIDSON, JR

RINGING ARRANGEMENT FOR MULTIPLEX CIRCUITS Filed sept. 24, 1919 2Sheena-sheetv 1 IN VEN TOR.

lull v Bfavb'dSO/@Jm ATTORNEY Jlyl, 1923. 1,463,200

J. DAVIDSON, JR

RINGING ARRANGEMENT FOR MULTIPLEX CIRCUITS Filed'sept. 24, 1919 2sheets-sheet 2 IN VEN TOR.

ATTORNEY k Patented July 31, 1923.

UNITED STA-,Tas

1,463,200 PATENT oFFIcE.

J'OHN-NAVIDSON, 'I'B,.,.VOFl HONTCLAIR, NEW JERSEY, ASSIGNOB TO AMERICANTELE- PHONE AND TELEGBAPH COMPANY, A CORPORATION F NEW YORK.

'BINGING @RANGEMENT Fon mULTTrLEx CIRCUITS.

Application illed September 24, 1919. Serial No. 325,824.

To all whlom it may concern.'

Be it known that I, JOHN DAVIDSON, Jr., residing at Montclair, in thecounty of Essex and Statev of New Jersey, have invented certainImprovements in Ringin Arrangements for Multiplex Circuits, o l'whichthe following is a specification.

. This invention relates to multiplex systems employing'carrier currentsand more particularly to arrangements whereby ringing-orother signalingcurrents may be transmitted o ver the channels of such a system.

. Oneof the features of this invention resides in the provision in acarrier system of 'a special amplifier 4for amplifying ringing currents-received from the carrier transmission 'circuit, so 'that theampllfcation of said ringing currents may be adjusted to any desireddegree independent of the amplification desired for telephonie or othersignaling currents.

v Another feature of the invention resides in the provision of an arranement in the low frequency line or circuit or controlling thel relaying'of ringing currents in either direction at the junction -point of thelow fre- I quency line or circuit with the carrier sys- These' features,together with other features of the' invention, which will more fullyappear-hereinafter, may be realized in accordancewith the detailedarrangement set forth in the following description and illustrated inthe accompanying drawing, Figures 1 4and 2 of which constitute circuitdiagrams of two embodiments of the invention .and Figure 3 .of whichillustrates a'circuit arrangement of a form of oscillator which maybe.employed for supplying ringing curren In 'Fi re 1 ML designates a mainline or circuit, or the transmission of carrier currents. Commontransmitting and receiving circuits TL and RL are associated with themainline ML through a balanced transformer 10. In order that thecircuits TL 'and RL ,may be rendered conjugate so that electrical.disturbances in the one will be 1vivithouteect upon the other, the mainline is balanced -worh L designates a low uency signaling line orcircuit, which, in common with a plurality of other lines, is adapted totransmit signals over the mainf line 11H1. 111 .the

`by an artificial line or net-' case illustrated, the line L, vis anordinary low frequency telephone circuit. The line L, is associatedthrough the transformer 11, with an outgoing carrier transmissionchannel TL, and an incoming carrier receiving channel 'RLP These twochannels are rendered substantially conjugate by roviding an artificialline or network N, for balancing the line L,. The channels TL, and RL,are

associated with the'fcommon circuits .TL and RL through filters TF', andRF, respectively. Similar channels corresponding to other low frequencysignaling clrcuits ma be associated with the circuits TL and RL thecarrier frequency assi ned.to the channel, the bands being of su cientwidth to accommodate the frequency variation due to the modulation ofthe basic carrier'ffrequency by the si naling frequencies; The

bands transmitte by the filters-TF', and

RF, may in practice be the same. The bands transmitted b l otherfilters, such as' TF', and RF,"v shou be sufficiently remote from thebands transmitted by the filters TF', and RF, to` allow, for frequencyseparation 1 ltween the channels.

The transmitting channel TL, includes a modulator M a band filter TF andan amplifier TA,. The modulator any-well-known type, but is illustrated'as a duplex vacuum tube modulator of the ty illustrated and describedin the U. S. app 1- cation ofJohnR. Carson, Serial No. '157 ,413,

filed March 25, 1917. The modulator is suplvf, may be of` of the broadplied with carrier currents of the frequency assigned to the channel,over a circuit 12. Thearrangement is such that carrier curl rentsare nottransmitted by the' modulator unless the circuit is unbalanced, due tothe ap lication of signaling current thereto.

he filter TF, is a band filter of the type disclosed in the Campbellpatents above referred to and is desied to suppress low frequencies andass t e carrier frequencies. 'llvhc amlifier A, may loe of any1 4well-'own taracter, but is preferably a duplex aan vacuum tube amplifier,which, as is welllmown, provides a minimum degree of. distortion at highfrequencies and hence is lli well adapted for the amplification ofcarrier currents.

The receiving orincoming channel RL, includes a detector or demodulatorD,. This demodulator may be of any Well-known type, but is preferably aduplex vacuum tube modulator of the general character illustrated anddescribed in the U. S. application of John R. Carson, Serial No. 157,-414, filed March 26, 1917. The duplex demodulator described in the saidCarson application operates upon the so-called homodyne method ofreceiving and consequently is supplied from the circuit 13 withoscillations of the carrier frequency assigned to the channel. Theoscillations supplied from the'circuit 13 react in a well-known mannerwith the received modulated currents, to detect the low frequencysignaling currents.

The channel RL, also includes an amplifier RA, and a filter RFQ. Theamplifier ltA, is preferably a vacuum tube amplifier as illustrated, andserves to amplify the detected signaling currents. The filter RTF', maybe of the general type illustrated in the above mentioned patents toGeorge A. Campbell and is preferably so designed as to transmit a rangeof frequencies extending from Zero up to the highest frequency emplo edin ordinary telephonie transmission.v

ince it is generally customary to ring over lines such as L, atrelatively low frequencies, such for instance as 16 cycles per second,it is desirable that some apparatus should be provided at the junctionbetween the lowQfrequenoy line and the carrier system, to translatethese ringing currents into ringing currents of some higher frequencywhich is more suitable for the modulation of carrier currents. lt hasgenerally 'been found that ringing currents having a frequency of 133cycles is adapted to this purpose, although it'will be understood thatother frequencies may be used, if preferred. lin order to produce thetranslation in ringing frequency above referred to, the line L, isAprovided with.v a ringing responsive relay 1li associated with the lefthand winding of a transformer 15. Said relay 14 controls aV relay 16,whereby ringing current from a source RS may be applied to the junctionpoint of the line L, with the transformer 11, so that ringing current istransmitted through said transformer to the outgoing carrier channelTL,. The 133 cycle 4.ringing source RS may be of any wellknowncharacter, but is preferably an oscillating vacuum vtube arrangementsuch as' illustrated in Figure 3. Form-reasons of economy it isdesirable that this ringing source should supply ringing current for a cincarico plurality of signaling circuits and consequently its outgoingcircuit 17. is provided with parallel connections leading to thecontacts of relays such as 16 for a number of diderent circuits.

ln order to provide for relaying ringDing currents incoming from themain line dL to the line L, a circuit 18 leading to the input of anamplifier A, is connected to the right hand winding of the transformer15. The circuit 18 is turned by means of the condenser to respond to 133cycles. A ringing responsive relay 19 is associated with the outputcircuit of the amplifier A, and controls the circuit of a relay 20 whichapplies 16 cycle ringing current to the line L, over its front contactsand simultaneously short circuits the outgoing channel TL, in order toprevent the transmission thereto of 133 cycle ringing currentv incomingfrom the channel RL,. TheI relay 19 controls the relay 2O through a slowacting relay 21 which, when it functions to close the circuit of therelay 20, simultaneously opens the circuit of the relay 16 to prevent afalse operation of said relay. The relay 16 is also so arranged thatwhen actuated to apply ringing current to the channel TL, it preventsthe de-energization of the slow acting relay 21, so that it isimpossible to complete a circuit over the relay 20.

The operation of the arrangement of lF igure 1 is as follows: Talkingcurrents incoming from the line L, are transmitted through thetransformer 11 to the circuit TL, and are impressed upon the modulatorM,. High frequency carrier currents from the circuit 12 are nowmodulated by the modulator M, in accordance with the talliing currentsand the modulated high frequency currents are transmitted through thefilter Tll` amplified by the vamplifier TA, and then transmitted throughthe lter TF, to the common circuit TL. These -modulated carrierfrequencies, together with modulated carrier frequencies from otherchannels simultaneously impressed upon the circuit TL, are transmittedthrou h the transformer 10 tothe main line ML. Vlodulated carriercurrents incoming from the y line ML, having the ro er frequency, areselected by the filter from the circuit RL and impressed upon thedetector D? As a result of the reaction of the received carrier currentsand the unmodulated carrier currents from the circuit 13 in the detectorl) the low frequency talking currents appear in the output circuit ofsaid detector, and are impressed upon the amplifier RA,. After beingamplified the low frequency currents are transmitted through the filterlill', to the main line L,.

Sixteen cycle ringing current incoming from the line L, actuates theringing responsive relay 1d which at its lower front contact completesthe circuit froml ground over thenormally closed contact of relay 21,

front contact of relay 14 and throughthe winding of relay 16 to battery.Relay 16, at its front contacts connects 133 cycle ringing current tothe right Winding of the transformer 11 and said ringing current istransmitted through the transformer 11 to the outgoing carrier channelTL1. The relay 16 at its lower front contact also connects ground to theWindingv of the slow acting I' relay 21, thereby preventing thev saidslow acting rela from being cle-energized, due to the chattering of thecontacts of the ringing responsive relay 19:' Relay 21 is therefore heldactuated and prevents vfalse operation -of the relay 20. The 133 cycleringingcurrent transmitted to the channel TL1 is limpressed upon rtheinput of the modulator M1 and modulates carrier current from the circuit12. The modulatedgoarrier vcurrent is then transmitted through thefilter TF1, amplified byl lthe amplifier TA1 and passed through thefilter TF 1 to the common circuit TL, from which it is transmittedthrough the transformer 10 to the main line ML.

Carrier currents modulated in accordance with rin ing currents `andtransmitted over the line froma distant station, are impressed -upon thecommon circuit RL and are selected through the filter RF1 and impressedupon the -input circuitA of the vde-l niodulator D1. The modulatedcarrierfrequencies react with carrier currents from the circuit 13, sothat 133 cycle ringing cur'- rents appear in the output circuit of thedemodulator D1. These 133 cycle ringing currents are amplified lby theamplifier BA1 and transmitted through thefilter RF1 and over thecontacts of the relay 16 to the circuit 18. From the circuit 18' the 133cycle ringing currents are assed tothe amplifier A1 which amplifies t eringing currents so that the amplified currents actuate the ringingresponsive relay 19. The actuation of this relay causes thede-energization ofthe slow acting relay 21 which disconnects ground from-the circuit of the relay 16' to prevent a false operation and connectsground to thel circuit of relay 20. Relay 20 is therefore energized andapplies 16 cycle ringing currents over its front contacts to the -lineL1. At the same time it short circuits the channel TL1 at its upperfront contact to prevent the transmission of 133 cycle ringing currentfrom the circuit RL1 to the circuit TL1.

In the arrangement which is described it will be noted that the meansfor relaying the ringing currents in both directions is associated with-the low frequency line L1. A modification of the invention isillustrated 'in Figure 2, in which the 133 cycle ringing current isapplied to and taken o from the carrier channels. In this figure a relay22 responsive to 16 cycle ringing current is bridged across the line L1land controls,

through a slow acting relay 23, a relay 21 which applies ringing currentvto the input connection of the modulator M1 from the 133 cycle ringingsource RS. The relay 24 is also arranged to short .circuit the inputwinding of the amplifier RA1 toprevent the transmission of 133 cycleringing current from the detector D1.

In order to provide for relayin rin ing currents incomingl from the mainine L, the circuit 25 leading to the input of the amplifier A1 isassociated with the secondary Winding of a transformer 26. The amplifierA1 is arranged to amplify 133 cycle ringing current coming ,from lthedetector D1 and controls, through its output circuit, a relay 27responsive to 133 cycle ringing current. Relay 27, through a, slowacting relay 28,

vcontrols a relay 29, whereby 16 cycle ringing 23. The 'slow actingrelay 23 thereb energizes relay24 which connects 133 cyc e ring-v ingcurrent from a source RS to the input connection of the modulator yM1.Ringing.

current applied to the modulator modulates A the carrier current fromthe source 12 and TF1 to the common transmitting circuit TL, from whichthey are impressed upon the line ML through the' transformer 10.

Carrier frequencies modulated by 133 cycle ringing currents at thedistant station, after being transmitted over the line. ML, areimpressed upon the common receiving circuit RL and passed through thefilter RF1 to the input circuit of the demodulator D1. Detected 133cycle ringing currents now appear inv the output circuit of saiddemodulator and after being amplified by the amplifier RA1 are impressedthrough the circuit 25 upon the amplifier A1, which is adjusted tosecure proper amplification for 133 cycle currents to operate the relay27. The operation of relay 27 opens the circuit of `the slow actingrelay y28, whiclL in turn closes the circuit of the relay 29. *Relay 29,over its front contacts, applies 16 cycle ringing current to the line L,and simultaneously short circuits the channel TL1 over its up`I frontcontact closed a short circuit connection across the input of theampliier BA1. in the receiving channel RLP lThis prevented thepossibility of the transmission of 133 cycle current over the channelTL,Y into the common `circuit TL through they transformer l() back intothe common receiving circuit RL and through the receiving channel lili,to the relay 27, consequently no false operation ofthis relay canresult. 4

By the provision of a supplemental amplilier for the ringing currentreceived over the carrier transmission circuit, the received ringingcurrent ma be amplified to any desired degree suitable for operation ofringing responsive apparatus. rlhe amplier RA, is not satisfactory for'this purpose, since When this amplifier isadjusted to secure the properamplification for telephone currents it does not suiciently amplify thereceived ringing currents. llt Will be obvious that the generalprinciples herein disclosed may be embodied in' many other organizationswidely diderent from those illustrated, without departing from thespirit of the invention as defined in the following claims.

What is claimed is:

1. ln a multiplex carrier system, a signaling circuit, av circuit forthe transmission of alternately carrier currents, an incomin carrierchannel for interconnecting said circuits, said channel including meansfor translating carrier currents into signaling currents, an ampliier insaid channel for amplifying signaling currents, another amplifierassociated with said channel for ampliiyin'g ringing 'currents incomingfrom said carrier transmission circuit, and means responsive-to ringingcurrents amplified by said second mentioned amplifier for applyingringing currents to said signaling circuit.

2. lln a multiples carrier system, a signaling circuit, a circuit forthe transmission of alternating carrier currents, outgoing and incomingcarrier channels interconnecting said circuits, saidchannels includingmeans tor translating signaling currents into carrier currents, and viceversa, means responsive to ringing current incoming from said signalingcircuit for applying ringing current to said outgoing channel, an amliier in said incoming channel for amplifyingl signal'- current, asecond amplilier associated said channel for amplifying ringin currents,andv means responsive to ampli,` ed ringing currents-.incoming from,said carrier transmission lcircuit tor applysponsive to ringing currentincoming from said incoming carrier channel to apply ringing current tosaid signaling circuit.

4. ln a multiplex carrier system, a signaling circuit, a circuit for thetransmission of alternating carrier currents, outgoing and incomingcarrier channels interconnecting said circuits, said channels includingmeans for .translating signaling currents into carrier currents, andvice versa, means associated with said signaling circuit and responsiveto ringing currents incoming from said circuit to apply ringing currentsto said outgoing 'carrier channel, means associated with said signalingcircuit tor am liitying ringing currents incoming from sai incomingcarrier channel, and means res onsive to such amplified ringing currentsor applying ringing current to said signaling circuit.

5. lln a multiplex carrier system, a signaling circuit, a circuit forthe transmission ot-alternating carrier currents, outgoing and incomingcarrier channels interconnecting said circuits, said channels includingmeans for translating signaling currents into carrier currents, and viceversa, a relay associated with said signaling circuit and responsive toringing current incoming from said signaling circuit to control theapplication oiE ringing current to said outgoing carrier channel, meansassociated with said signaling circuit to amplify ringing currentincoming from said incoming carrier channel and a ringing responsiverelay associated with said amplifyin means for controlling theapplication o ringing cunrent to said signaling circuit.

6. lln a multiplex carrier system, a signaling circuit, a circuit forthe transmission oit alternating carrier currents, an incoming carrierchannel interconnectin said circuits, said channel including means ortranslatin carrier currents into signaling currents, an

an amplifier associated with said signaling circuit for amplifyingringing currents incoming from said carrier channel.

7. lln a multiplex carrier system, a signaling circuit, a circuit forthe transmission of alternating carrier currents, an incoming carrierchannel interconnecting said cirt8@ cuits, said channel including meansfor translating carrier currents into signaling currents, an amplifierfor amplifying signaling currents incoming from said carrier e channeland a second amplifier for amplifying ringing currents incoming fromsaid channel.

8. n a multiplex carrier system, a signaling circuit, a circuit for thetransmission of alterte Dating carrier currents, an incoming carrierchannel interconnecting said circuits, said channel including means fortranslating carname to this specification this 231' rier currents intosignaling currents, an amplifier for amplifying signaling currentsincoming from said carrier channel, a second amplifier for amplifyingringing currents incoming from said carrier channel, and meanscontrolled by said second mentioned amplifier for applying ringingcurrents to said signaling circuit.

In testimony whereof, I have si ed my ay of September 1919.

JHN 'a i SON, JR.

